Cylindrical section casing supported water tube boiler



Sept. 16, 1958 T. s. SPRAGUE 2,852,002

CYLINDRICAL SECTION CASING SUPPORTED WATER TUBE BOILER Original FiledDec. 7, 1953 S.H.OUTLET HDR. 96

2 Sheets-Sheer. 1

SHJNLET HDR.

COAL BUNKER COAL SCALES PRODUCT GAS OUTLET COAL FEEDER POCKET SEALER F16 1 INVENTOR.

THEODORE s. SPRAGUE ATTORNEY Sept. 16, 1958 2,852,002

CYLINDRICAL SECTION CASING SUPPORTED WATER TUBE BOILER I T. S. SPRAGUEOriginal Filed Dec. 7, 1953 2 Sheets-Sheet 2 F 3 3 INVENTOR.

THEODORE ssmmsus d44- ATTORNEY United States Patent ice CYLINDRICALSECTION CASING SUPPORTED WATER TUBE BOILER Theodore S. Spragne, Hewlett,N. Y., assignor to The Babcock & Wilcox Company, New York, N. Y., acorporation of New Jersey Original application December 7, 1953, SerialNo. 396,696. Divided and this application November 2, 1955, Serial No.544,397

8 Claims. (Cl. 122-333) This invention relates to fluid heat exchangeapparatus and, more particularly, to such apparatus including anelongated setting or unit of circular cross-section including anelongated furnace chamber of circular cross-section and a novel interiorarrangement of gas passes and heat exchange surfaces. This applicationis a division of my copending application S. N. 396,696, filed Decembet7, 1953.

As stated in my copending application, the invention apparatus isparticularly adapted for use with two zone reaction process andapparatus described and claimed in the copending application of P. R.Grossman and T. S. Sprague, Serial No. 225,346, filed May 10, 1951, nowPatent No. 2,801,158, for Method of and Apparatus for Gasification ofPulverized Coal, now U. S. Patent No. 2,801,158, issued July 30, 1957,and will be described with particular reference to the process andapparatus of such application. it should be understood, however, thatsuch particular cooperation is exemplary only, and not by way oflimitation, as the invention apparatus is useful with other synthesisgas reactors as well as with other combustion arrangements.

The reaction of the pulverized coal with steam and CO is endothermic innature, thus requiring a net heat input to raise the temperature of thereactants to the optimum reaction temperature range. This temperatureincrease may be effected by an initial exothermic reaction involvingpartial combustion of the coal utilizing a quantity of oxygeninsufficient for complete combustion.

The most effective temperature range for the endothermic reaction is inexcess of 2000 F., and the combustion temperature must be substantiallyabove this range to insure that enough sensible heat be imparted to thereactants to maintain the temperature in the range during whichgasification progresses rapidly.

As a result of these foregoing considerations, the temperature of thesynthesis gas produced is relatively high and may be of the order of2000 F. or more. The sensible heat of the exiting gases must beextracted to cool the synthesis gas to a much lower handlingtemperature, for example, of the order of 400 F.

The use of a superheated steam generator to extract heat from thesynthesis gas is particularly advantageous in a gas synthesis processutilizing coal, such as that described and claimed in said copendingapplication of Grossman and Sprague. In such case, the steam generatornot only provides a supply of superheated process steam at a controlledoptimum temperature but also reduces the temperature of the deliveredsynthesis gas to an optimum low value to assure a good overall thermalefficiency of the unit and provides a supply of steam generally inexcess of the synthesis process requirements so that steam is availablefor other process or power work. For the foregoing reasons, a steamgenerator is preferably integrated with the synthesis gas reactionchamber or unit, and is disposed in the flow path of the gasesleavassastz Patented Sept. 16, 1958 ing the reaction chamber to extractheat from such gases to generate steam.

The reduction of the solid fuel to the pulverized state for use in thegasification process requires power, such pulverizing being convenientlyeffected by a steam-driven pulverizer. Accordingly, steam from the steamgenerator is used in the pulverizing of the solid fuel, as by powering aturbine for driving a pulverizer. The exhaust steam from the puverizingoperation is reheated in a steam heater, or superheater, which may beseparately fired but which is preferably disposed in the flow path ofthe synthesis gas. This reheated steam is then utilized as a conveyingmedium to feed the pulverized fuel from the pulverizer to thegasification or reaction chamber or unit.

Normaliy, mechanical pulverizers are air-swept to convey the pulverizedfuel from the pulverizer to burners. in accordance with the presentinvention, the reheated steam is used to sweep the pulverizer withsteam, rather than with air, and thus convey the pulverized fuel to theburners in suspension in a fluid stream of the reheated or superheatedsteam. The steam thus utilized to carry the pulverized fuel alsoprovides the steam requirements of the gasiiication process. Preferably,saturated steam at a relatively high pressure is utilized to drive theturbine for the pulverizer, and the exhaust steam from the turbine isfed to a superheater where it is heated to a high temperature, but at arelatively low pressure. This superheated, relatively low pressure,steam is then fed through the pulverizer to entrain the pulverized fueland convey it into the reaction unit, where the oxygen-containing gas isadmixed with the steam and coal for the synthesis gas reaction.

The present invention is directed more particularly to the novel settingof the steam generator and the arrangement of gas passes and heatexchange surfaces therein.

For an understanding of the invention principles, reference is made tothe following description of a typical embodiment thereof as illustratedin the accompanying drawings.

in the drawings:

Fig. 1 is a partially schematic vertical elevation view of an integratedsynthesis gas reaction unit and steam generator and superheaterembodying the invention;

Fig. 2 is a horizontal sectional view of the invention apparatus takenon the line 2-2 of Fig. 1; and

Fig. 3 is a partial vertical elevation View of the apparatus of Fig. 1taken on a plane at right angles to the plane of Fig. 1;

Referring to the drawings, the reaction unit 30 and the steam generator50 associated therewith are substantially completely enclosed within anupright elongated cylindrical metal shell 10 having a layer of suitableheat insulation material 11 covering its outer surface. The assembly issuspended, for downward thermal expansion, from a suitable supportingframework (not shown), this sus pension preferably being effected byhangers secured to the framework and to brackets on shell 10. At itslower end, shell 10 has an outwardly offset portion 18 merging with ahopper shaped bottom portion 21. Portion 21 is connected, by anexpansion joint 22, to a smaller diameter cylindrical metal shell 23having a refractory lining Z4 constituting a slag disposal well,collection receptacle, or ash can 20 receiving slag from reaction unit30 through a slag outlet 15. The slag disposal chamber contains asuitable liquid, such as water, which chills to a solid the molten slagdripping into the liquid from outlet 15. The solidified slag may beremoved from slag receptacle 20, either continuously or periodically, bya suitable slag conveyor, or conventional type, generally indicated at25.

In a manner described more fully hereinafter, the interior surface ofshell 10 is lined with shell protecting tubes 51 forming part of thesteam generator 50 and arranged as a cylindrical, of circularcross-section, bank substantially covering the inner surface of shelland defining and generating chamber. The tubes 51 are connected, attheir lower ends, into interconnected annular headers 52 and 53 and, attheir upper ends, into the steam and water drum 55 of generator 50.Adjacent headers 52 and 53, some of the tubes 51 are inwardly offset andexposed to form a support for the refractory floor or bottom of reactionunit 30', to define part of the slag outlet and absorb heat from theslag and any gases flowing through outlet 15. The upper inner peripheryof the offset tube portions support a water cooled monkey coil 28 actingas a slag drum for forming the refractory bottom or floor of reactionunit 30 and further defining the slag outlet.

The refractory floor of reaction chamber 39 may be of any suitablerefractory material. For example, it may comprise packed refractory 31covering the offsets of tubes 51 and arranged to receive slag 33. Therefractory wall lining 32 of chamber 30 may likewise be of any suitabletype. For example, it may comprise plastic refractory packed againststudded portions of tubes 51 and covered by built-up layers ofrefractory shapes.

The combustible reactants are introduced into reaction unit 30 throughburners 35. In the arrangement shown, a plurality of burners 35 arearranged to extend into re action unit 30 in circumferentially spacedrelation at a zone substantially at the dividing line between upper andlower wall lining sect-ions. These burners are so arranged that theiroutlets are directed downwardly, and preferably radially toward slagoutlet 15, so as to facilitate the maintenance of the temperature at theslag outlet at a value sufficiently high to assure the slag remainingfluid to flow through outlet 15 and into collection receptacle 20. Asindicated at 57, certain of the tubes 51 are bent away from shell 10 atthe burner locations to provide the burner ports. These bent awayportions 57 also serve as an additional, support for the upper portionsof refractory lining 32 so that the portions of the refractory lining ofunit 30 below the burner level may be removed and replaced withoutdisturbing the upper portion of the refractory wall lining. This isadvantageous in practice, as, due to the eroding effect of the swirlingand burning gases in the lower portion of unit 30, replacement of thelower portion of the refractory wall is required more often than isreplacement of the upper portion of the refractory wall.

The burners 35, deliver the combustible mixture of a solid,carbon-containing fuel, in the pulverized state, steam, and anoxygenacontaininggas into the reaction unit 30. The oxygen-containinggas is provided in an amount less than that required for completecombustion of the fuel, and the reactants undergo an exothermic reactionin the lower portion of the unit 39 which raises the temperature of thereactants to the optimum range for'subsequent endothermic reaction ofthe steam with the products of the preponderantly exothermic reaction toform the synthesis gas. As fully set forth in said U. S. Patent ofGrossman et al., No. 2,801,158, the coal gasification or synthesis gasreaction is effected in two distinct zones, with a preponderantlyexothermic reaction taking place in the lower portion of unit 30 and apreponderantly endothermic reaction taking place in the upper portion ofunit 30. The level of the outlets of burners 35 represents the dividingplane or zone between these two reaction zones, the elevation of thezone of reactant admission, together with the downward firing toward theslag outlet, confining substantially all of the exothermic reaction tothat portion of reaction unit 30 located below the outlet burners.

The amount of oxygen contained in the oxygen-containing gas introducedthrough burners 35 is dependent upon the desired chemical make-up of thesynthesis gas. For example, in producing a synthesis gas which consistsessentially of H and CO, useful in synthesizing hydrocarbons, theoxygen-containing gas may comprise commercially pure oxygen, which issubstantially 99% 0 On the other hand, if the synthesis gas produced isintended for use in synthesis of ammonia, a substantial portion ofnitrogen may be included in the oxygen-containing gas, this proportionranging up to the usual 79% N percentage normally present in theatmosphere. Preferably, and particularly in the present invention, thepulverized fuel is introduced through the burner in a stream of hightemperature steam. The oxygen-containing gas is also introduced throughthe burners, but is adm xed wi h the f l and st m ly at he exi or outlof each burner. The burners are provided with a liquid coolantcirculating system, for heat protection, with the coolant supply beingcommon with that for coil 29.

The pulverized fuel is delivered to burners from a suitable mechanicalpulverizer generally indicated at 40 and which may be any conventionalmechanical pulverizing construction Well known to those skilled in theart. This pulverizer, insofar as the present invention is concerned,includes outlet conduits 41 which are connected to the several burners35 and, in a manner to be described, the pulverizer is swept by steam toentrain the pulverized fuel and deliver it to burners 35 fluid borne inthe stream. The fuel to be pulverized, coal, coke, lignite, peat, orother solid carbonaceous fuel, is supplied from a hopper 42 to scales 43from which it is delivered to feeders 44. These feeders deliver the fuelto a pocket sealer 46 of known construction, which delivers the fuel tothe inlet 47 of pulverizer 40 While maintaining the pulverizerpressure-sealed. In the arrangement shown, pulverizer 40 is driven by asteam turbine supplied with steam from steam generator 50, all in amanner described more fully hereinafter.

The steam generator 50 includes the liquid and vapor drum 55 extendingtransversely of the upper end of shell 10 and covered with theinsulationll. The axis of drum 55 is otfset somewhat from a diameter ofshell 10, and the drum is disposed in, and closes, an opening in the topof shell 10. A convection type steam generating Section 60, comprising aplurality of substantially parallel liquid and vapor containing tubes61, connects the liquid space of drum 55 into a much shorter drum 65forming the liquid drum of the steam generator. Drum 55 is suspended,through the medium of U-shaped hangers, from the structural frameworkand support drum 65 through the medium of convection section 60.

Downcotners 62 extend between the liquid space of drum 55 and theannular headers 52 and 53, these downcomers being preferably locatedexteriorly of shell 10 and connected into the ends of drum 55. Asstated, the upper ends of the shell protecting tubes 51 are alsoconnected into the liquid space of drum 55, with the portions oftubes 51above the upper edge of the refractory lining of unit 30 being exposedto the hot gases to form a radiant heating section.

At an elevation a short distance above the upper end of the refractorylining of unit 30, alternate tubes 51 are bent inwardly away from theinner surface of shell 10 to define the gas passes for the steamgenerator and to form a slag screen 64 in front of a superheater 70.This superheater, shown as a pendant type by way of example only,comprises serial looped tubes 71 connecting a superheater inlet header72 to the superheater outlet header 73. The superheater tubes 71 extendthrough the upper end of shell 10 to connect into the headers 72 and 73,which are disposed in a chamber formed by an arched section 74 ofinsulation 11, this arched section extending substantially parallel to,and laterally offset from, drum 55.

The alternate tubes 51 bent inwardly away from shell 10 may be suitablyenlarged to form the bafies defining the gas passes for generator 50, ormay be enlarged and also provided with plate studding to define'thebaflies.

aeaaoo J These bent tubes form a first or wing bafiie 63 which slopesinwardly and upwardly to deflect the hot gases toward the slag screen64. The inner end of baffle 63 supports a pier 67 engaging lower drum65, and which may be formed of cast refractory or built up of refractoryshapes.

As best seen in Figs. 2 and 3, the bent-in tubes 51 also provideparallel, vertical side baflies 76 embracing the ends of lower drum 65and defining a gas pass 75 which is substantially rectangular in plan.Gases enter pass 75 through slag screen 64 and flow across superheater70 and convection section 60, and thence into an outlet 77.

The outlet 77 is formed by bending alternate tubes 51 away from theinner surface of shell 10, as indicated at 81. The outlet 77 directs thegases into a short conduit section 82 extending outwardly and downwardlyfrom shell 10, and joined by an expansion joint 83 to a conduit section84 directing the relatively cooler gases over an economizer 80 disposedin a casing 86 supported on the main supporting framework. Water isadmitted to the economizer section through an inlet header 91 at thelower end of the economizer, flows upwardly through the economizer andinto an outlet header 92 at the upper end thereof, from which it isdelivered to the liquid drum 65, the connection therebetween beingomitted to simplify the drawing. The relatively cooled gases aredelivered from casing 86 to a product gas outlet 93 communicating withthe lower end of casing 86. A small conduit 94 extends from outlet 93into slag collection receptacle 20 through the refractory lining section27, this conduit being provided with a damper 90. By means of dampercontrol conduit 94 a draft is created through slag outlet 15 so as toeffect a controlled bleeding of hot gases from reaction unit 30 throughslag outlet 15 to maintain an adequately high temperature at the slagoutlet.

In accordance with the present invention, saturated steam from theliquid and vapor drum 55 is utilized to power turbine 45. This steam isdirected to turbine 45 through a saturated steam line 95 connected tosaturated steam outlet 95. Another saturated steam line 96 is branchedfrom steam line 95 so that steam generated, in excess of that requiredto power turbine 45 and to meet the process steam requirements, may bedelivered to another point of utilization, line 96 being known as aby-product steam line. Exhaust steam from turbine 45 is fed by a line 97to the inlet header 72 of superheater 70. The reheated or superheatedexhaust steam is taken from superheater outlet header 73 by a line 98connected, through the carrier fluid inlet of pulverizer 40 to thepulverized fuel space of the pulverizer. This reheated or superheatedsteam sweeps the pulverizer fuel and steam to burners 35. To provide forthe case in which the steam requirements of turbine 45 are less than theprocess steam requirements, a by-pass connection 99 controlled by avalve 100 interconnects saturated steam supply line 95 and exhaust orreturn line 97. Thereby, the steam required by the process, in excess ofthat required to operate turbine 45, can by-pass the turbine fordelivery to superheater 70.

The operation of the invention will best be understood by referring to atypical practical embodiment thereof. In this embodiment, pulverizedcarbonaceous fuel entrained in steam, and at a temperature ofapproximately 250 F. dependent upon the moisture content of the fuel, isdelivered from burners 35 at a pressure of approximately 4 p. s. i. g.,being admixed with commercially pure oxygen at the exits of burners 35.In the preponderantly exothermic reaction of the oxygen, carbon andsteam in the lower portion, or primary chamher, of reaction unit 30, thetemperature of the reactants is raised to a value substantially inexcess of 2,500 F., and after the preponderantly exothermic reactionbetween products of combustion and the steam, which takes place in theupper half, or secondary chamber, of

somewhat cooled gas flows through slag screen 64 and;

through gas pass 75, across superheater 70 and convection section 60.These heat absorption elements are so designed that the temperature ofthe gas leaving through the product gas outlet 93, after heat transferto economizcr 80, is substantially 400 F.

In the particular illustrative example, extraction of heat from thesynthesis gases generates approximately 14,000 pounds per hour ofsaturated steam at 250 p. s. i. g. The process steam requirements areapproximately 6760 pounds per hour of superheated steam. Consequently,this amount of saturated steam is delivered to turbine feed line at atemperature of approximately 406 F., and the balance of the steam,amounting to 7240 pounds per hour, is delivered as by-product steamthrough line 96. Turbine 45 requires 2700 pounds of saturated steam perhour, so that 4060 pounds per hour are.delivered from line 95 to exhaustline 97 through by-pass 99 by adjustment of valve 100. In driving theturbine, the pressure of the saturated steam is reduced to p. s. i. g.,and the exhaust and by-pass steam at substantially this pressure isdelivered to superheater inlet header 72. In

superheater 70, the exhaust and by-pass steam is raised I to 750 F. at10 p. s. i. g., and this steam is delivered by line 98 to pulverizer 40to sweep the pulverizer and en-' train the pulverized fuel for deliverythrough burners 35. The latter are supplied with oxygen, in thisexample, through feed lines generally indicated at 105.

The foregoing illustration is exemplary only and the steam balance wouldbe substantially different for an other installation, depending upon thedesired synthesis gas output and other factors. Also, and as statedhereinafter, the oxygen-containing gas may be a mixture of oxygen andnitrogen, for example, rather than commercially pure oxygen, dependingupon the ultimate use of the synthesis gas. While a specific embodimentof the invention hasbeen shown and described in detail to illustrate theapplication of the invention principles, it will be understood that theinvention may be embodied otherwise without departing from suchprinciples.

What is claimed is:

1. Fluid heat exchange apparatus comprising, in combination, wall meansforming an elongated enclosure of circular cross-section; means formingan elongated furnace chamber of circular cross-section within saidenclosure; means for burning a fuel in said furnace chamber; wing bafliemeans extending partially across substantially parallel enclosure fromthe longitudinal wall thereof; means, including said wall meansextending upwardly from said wing baflle means and chordally of saidenclosure, and said bafile means, forming a lateral heating gas pass incommunication with said chamber; upper and lower pressure vesselcomponents in said enclosure; and fluid heating tubes disposed in saidgas pass interconnecting said components transverse to the gas flow insaid gas pass.

2. Fluid heat exchange apparatus comprising, in combination, wall meansforming an upwardly elongated enclosure of circular cross-section; meansforming an upwardly elongated furnace chamber of circular crosssectionwithin said enclosure adjacent the lower end thereof; means for burninga fuel in said furnace chamber; wing bafile means extending partiallyacross said enclosure from the longitudinal wall thereof intermediateits ends; means, including said wall means and said baffle means,forming a lateral heating gas pass in communication with said chamber; agas outlet in said enclosure immediately above the outer end of saidwing baifie means; upper and lower pressure vessel components in saidens closure; fluid heating tubes disposed in said gas. passinterconnecting said components transverse to the gas flow in said gaspass; and fluid heating tubes constituting at least part of said wallmeans and said baflle means.

3'. Fluid heat exchange apparatus comprising, in combination, wall meansforming an upwardly elongated enclosure of circular cross-section; meansforming an upwardly elongated furnace chamber of circularcrosssectionwithin said enclosure adjacent the lower end.

thereof; means. for burning a fuel in said furnace chamber; baffle meansextending partially across said enclosure from the longitudinal wallthereof intermediate its. ends; means, including said wall. means and,said bafiie means, forming a lateral. heating; gas pass. incommunicationwith Said chamber; a gas outlet in said. enclosure abovesaid baffle. means; an upper fluid drum at the top of said enclosure; alower fluiddrumin said enclosure and completely within the lower part.of said gas pass; and convection, fluid heating tubes disposed in saidgas pass transversely of the gas flow therethrough and interconnectingsaid drums.

4. Fluid heat exchange apparatus comprising, in combination, wall meansforming an upwardly elongated enclosure of circular cross-section; meansforming an upwardly elongated furnace chamber of circular crosssectionwithin said enclosure adjacent the lower end thereof; means for burninga fuel in said furnace chamber; bafile means extending partially acrosssaid enclosure from the longitudinal wall thereof intermediate its ends;means, including said wall means and said baffle means, forming alateral heating gas, pass in communication with said chamber; a gasoutlet in said enclosure above said bafiie means; an upper fluid drum atthe top of said enclosure; a lower fluid drum in said enclosure andcompletely within the lower part of said gas pass; convection fluidheating tubes disposed in said gas pass transversely of the gas flowtherethrough and interconnecting said drums; and radiant fluid heatingtubes constituting at least part of said wall means and said bafliemeans.

15. Fluid heat exchange apparatus comprising, in com bination, wallmeans forming an upwardly elongated enclosure of circular cross-section;means forming an upwardly elongated furnace chamber of circularcrosssection within said enclosure adjacent the lower end thereof;means. for burning a fuel in said furnace chamber; bafile meansextending partially across said enclosure from the longitudinal wallthereof intermediate its ends; means, including said. wall means andsaid baflie means, forming a lateral heating gas. pass in communicationwith said chamber; a gas outlet in said enclosure above said bafllemeans; an upper fluid drum at the top of said enclosure; a lower fluiddrum in said enclosure and completely within the lower part of said gaspass; convection fiuid heating tubes disposed in said gas passtransversely of the gas flow therethrough and interconnecting saiddrums; a circular cross-section row of radiant fluid heating tubesconstituting; at least part of said wall means and connecteddirectlyinto said upper drum at their upper ends; certain.- of said radiantfluid heating tubes being bent inwardly intermediate their ends toconstitute at least part of said baflie means and to constitute upwardlyex.- tending walls, ofv said gas pass extending in parallel relationchordally to said enclosure; and means, including downcomer means,connecting the lower ends of said. radiant fluid heating tubes to saidupper drum.

6. Fluid heat exchange apparatus comprising, in combination, wall meansforming an. upwardly elongated enclosure of circular cross-section;means forming an upwardly elongated furnace chamber of circularcross-section within said enclosureadjacent the lower end thereof; meansfor burningya fuel in said furnace chamber, baflle. means extendingpartially across said enclosure from the longitudinal wall thereofintermediate its ends; means, including said wall means and said bathemeans, forming a lateral heating gas pass in communication with saidchamber; a gas outlet in said enclosure above said baffle means; anupper fluid drum at the top of said enclosure; a. lower fluid drum in.the lower part of said gas pass; convection fluid heating. tubesdisposed in said gas pass transversely of the gas flow therethrough andinterconnecting said drums; a circular cross-section row of, radiantfluid heating tubes. constituting at least part of said wall means andconnected into said upper drum at their upper ends; certain of said.radiant fluid heating tubes being bent inwardly intermediate. their endstov constitute at least part of said baflde means; and means, includingdowncomer means, connecting the lower ends of said radiant fluid heatingtubes to said upper drum; the inner ends; of said baffle forming .tubesbeing bent upwardly and connected into said upper drum to constitute atleast part of upwardly extending walls extending chordally of saidenclosure defining said lateral gas pass and to form a slag screenat theentrance of said pass.

7'. Fluid heat exchange apparatus as claimed in claim- 5 in which saidfurnacechamber is formed by a refractory lining on theinner sides of thelower portions of said radiant fluid heating tubes.

8. Fluid heat exchange apparatus as claimed in claim 5 including headermeans connected to the lower ends of said circular row of tubes anddowncomers connecting said'headermeans to saidupper drum.

References Cited in the file of this patent UNITED STATES PATENTS1,702,933 Dankset a1 Feb. 19, 1929 2,228,938 7 Wood Jan. 14,, 19412,672,849 Fruit Mar. 23, 1954' 2,686,500 Hauck Aug. 17, 1954

